1. Field of the Invention
This invention relates to apparatus for generating a parallel magnetic field within a magnetically shielded housing for testing magnetic sensors, such as direction indicator sensors for vehicle electronic compass.
2. Description of the Prior Art
In the prior art parallel magnetic field generators are known wherein current is passed through a cylindrically wound coil shielded against external magnetic fields by a housing made of an iron or permalloy plate, and wherein a sample to be tested is set in the parallel magnetic field thus produced and is externally rotated about an axis parallel to the magnetic field by a rotational direction converting mechanism which permits external readout of the rotational angle.
However, in such prior art parallel magnetic field generators the mechanism for rotating the sample is complicated. In addition, where gears are used for the rotational direction converting mechanism, it is difficult to improve the precision of the display of the angle of the sample with respect to the parallel magnetic field due to play between the gears. Furthermore, where an iron plate is used for the magnetically shielded housing, the shielding is limited. The iron plate has to be demagnetized, and the apparatus as a whole is heavy. Where a permalloy magnetically shielded housing is used, strain is liable to be produced at the time of manufacture.